Bromide compounds are of great commercial importance to several industries. Calcium bromide brines, for example, are used in oil well completion and workover fluids. Typically, while a well is being drilled, drilling mud (a suspension of solids such as barite, bentonite, or clay in water) is used to carry cuttings from the bit to the surface, to maintain sufficient hydrostatic pressure in the borehole to prevent a blowout, and to cool the bit and reduce friction between the drill string and the sides of the borehole. Most of these functions must also be performed during workover and completion operations, but drilling mud is unsatisfactory in those situations for several reasons. First, it contains a major amount of suspended solids, and the solid particles are detrimental to the workover and completion operations. Second, the mud is relatively expensive. Water by itself is not satisfactory either, in part because its specific gravity is not high enough. Calcium bromide does not have the drawbacks of mud, and as a completion fluid has a particular advantage in that solids free aqueous solutions of very high specific gravity can be made from it. Calcium bromide and other high density salt solutions used in this way are commonly known as clear brine fluids.
The present invention utilizes sodium bromide in the manufacture of ammonium bromide and calcium bromide. Sodium bromide brine is a waste product of some commercially used chemical processes, and thus is readily available. However, before the present invention, sodium bromide brine has often been disposed of, a practice which wastes the energy and effort expended to purify and concentrate the bromide ion. Sodium bromide has not generally been viewed as a potential feed stock for chemical processes. Now, instead of being thrown out, sodium bromide brine may be treated in accordance with this invention so that materials which in the past have been considered waste products may now be reclaimed and put to valuable uses.
Previous separation techniques have relied on oxidation of the bromide ion to bromine and separation from solution as a gas. Other methods of bromide concentration have been based on solvent extraction or ion exchange. The present invention relates to the recovery of the bromide ion as calcium bromide or ammonium bromide which are commercially useful.